The present invention relates generally to the art of tapping conduits and, more particularly, to the art of tapping mains and service lines for purposes of replacing same without interrupting service. The invention will be described in connection with gas mains and service lines, but those of ordinary skill in the art will quickly recognize that the invention has broader application to other mains and service lines, especially those designed to supply a fluid to a recipient in a non-interruptible fashion.
In the installation of new natural gas mains, it is typical to bury the new main in the desired location (usually in parallel with an existing main) and thereafter connect the existing or new service lines thereto for purposes of supplying gas to recipients by way of respective service lines. FIG. 1 illustrates a prior installation for the transmission of natural gas from a buried main conduit 10 to a home, business or other recipient 15. Gas is withdrawn from the main 10 through a main tee 12, and a gas service line 14 fluidically connects the branch passage of the main tee 12 to the recipient 15, typically by way of a meter (not shown). Because older gas mains and older service lines were typically fabricated from iron, these elements corrode and must be replaced. In each case, plastic conduit is a preferred replacement.
Often, the gas service line 14 is a plastic conduit that has been inserted into a preexisting iron or other metallic service line conduit 13 for the purpose of xe2x80x9cinsert-renewingxe2x80x9d the gas service to the recipient 15. In such an operation, the plastic conduit 14 is slidably inserted into the existing conduit 13 from the recipient end and the distal end of the plastic conduit is sealingly engaged with the existing metallic conduit adjacent the main 10 to prevent gas flow between the existing and new service line conduits. This insert-renewing operation has been found to be a highly effective and convenient means for replacing an obsolete service line conduit 13.
Heretofore, installation of a new main has involved simply cutting or blocking the relevant conduits and inserting the new conduits into the gas-flow circuit via tapping tees. For example, with continuing reference to FIG. 1, the service line 14 could be severed at the point 18 and thereafter connected to a new main. This, of course, interrupts service to recipients downstream relative to the cut 18. With gas transmission systems, interruption of service results in the extinguishment of pilot lights, and these must be re-lit by service personnel when gas service is restored. Furthermore, a significant amount of air often enters the gas transmission circuit and must be bled before the pilot lights will remain lit. The interruption of gas service during the main and/or service line replacement operation is highly undesirable and adds expense and inconvenience to the operation while lengthening the time recipients are without service.
Another deficiency associated with respect to prior main and/or service line replacement is that prior tapping tees are not well-suited for use on small-diameter plastic conduit, e.g., conduit with less than a two inch outer diameter. With conventional tapping tees, such conduit sometimes partially collapses during the tapping operation, and this prevents the formation of a good seal between the body of the tapping tee and the outer surface of the conduit.
In light of the foregoing specifically noted deficiencies and others associated with convention tapping tees and methods, it has been deemed desirable to provide a new and improved tapping tee and method that overcome these deficiencies and that provide better overall results.
In accordance with a first aspect of the present invention, a method of replacing an existing gas main that supplies gas to a recipient through an existing service line includes connecting a first tapping tee to a new gas main and connecting a second tapping tee to the existing service line. The first and second tapping tees are then fluidically interconnected with an interconnecting service line, and the new gas main is tapped with the first tee so that gas flows from the new gas main into the interconnecting service line up to the second tee. All air is then bled from the interconnecting service line between the first and second tees, and thereafter the existing service line is tapped with the second tee so that gas is supplied to the recipient through both the existing service line and the interconnecting service line. Gas flow to the recipient from the existing main is then terminated with no interruption of gas service to the recipient.
In accordance with another aspect of the invention, a tapping method for supplying fluid to a recipient from a new pressurized fluid main without interruption of service from an existing main and service conduit includes connecting a first conduit tap to a new pressurized fluid main, and connecting a second conduit tap to an existing service conduit in fluid communication with a downstream recipient. The first and second taps are fluidically interconnected with a connecting conduit, and the new pressurized fluid main is tapped with the first conduit tap. A bleed passage in the second tap is opened and fluid is bled from the new pressurized fluid main and connecting conduit until a desired bleed output is detected. The bleed passage is then closed and the existing service conduit is tapped with the second conduit tap.
In accordance with a further aspect of the present invention, a tapping tee includes a body member defining: (i) an internal threaded passage; and, (ii) a conduit-receiving bore in fluid communication with the internal passage. A cutter has an externally threaded region that cooperates with the threaded passage of the body member for advancing and retracting the cutter in response to its rotation, and the cutter further includes a cutting edge at a first end adapted to cut an opening in a conduit secured in the bore. The tee includes a branch passage in fluid communication with the internal threaded passage, and a selectively openable bleed passage for venting the branch passage to a location exterior of the tapping tee.
One advantage of the present invention is the provision of a no interrupt service tapping method for replacing gas mains and/or service lines without interrupting service to a downstream recipient.
Another advantage of the present invention resides in the provision of a gas line replacement method wherein the pilot lights in gas recipient""s appliances are not extinguished and need not be re-lit after the gas line replacement operation.
A further advantage of the present invention is the provision of a gas line replacement method wherein one hundred percent gas is delivered to the recipient through the new gas line immediately upon gas being delivered to the recipient through the new gas line.
Still another advantage of the present invention resides in the provision of an improved tapping tee specifically adapted for use in tapping relatively small diameter plastic conduit without collapsing same.
A still further advantage of the present invention is found in the provision of a tapping tee with a separate O-ring retainer.
A yet further advantage of the present invention resides in the provision of a tapping tee specifically adapted for tapping relatively small diameter plastic conduit, wherein the body of the tapping tee defines an ovalized bore for receipt of the conduit to be tapped, with the major (longer) axis of the bore arranged parallel to the tapping axis.
Another advantage of the present invention is found in the provision of a tapping tee that is specifically adapted for facilitating a gas bleeding operation.
Still other benefits and advantages of the present invention will become apparent to those of ordinary skill in the art to which the invention pertains upon reading and understanding the following specification.